Question 1

State whether the statements given below are True [T] or False [F]. Correct the false statement(s).

(i) Oxygen gas is more soluble in hot water rather than in cold water.
(ii) A mixture of sand and water is a solution.
(iii) The amount of space occupied by any object is called its mass.
(iv) An unsaturated solution has more solute dissolved than a saturated solution.
(v) The presence of different gases in the atmosphere is also a uniform mixture.

Accepted Answer

Answers:
(i) False. Oxygen gas is more soluble in cold water than in hot water.
(ii) False. A mixture of sand and water is not a solution; it is a suspension.
(iii) False. The amount of space occupied by an object is called its volume, not mass.
(iv) False. An unsaturated solution has less solute dissolved than a saturated solution.
(v) True. The atmosphere is a uniform mixture of different gases. — Step-by-step:
(i) Solubility of gases decreases with increase in temperature, so oxygen is more soluble in cold water.
(ii) Sand does not dissolve in water; hence, sand-water mixture is not a solution.
(iii) Mass is the amount of matter; volume is the space occupied.
(iv) Saturated solution contains maximum solute; unsaturated contains less.
(v) Gases in atmosphere mix uniformly forming a homogeneous mixture.

Question 2

Fill in the blanks.

(i) The volume of a solid can be measured by the method of displacement, where the solid is _______ in water and the _______ in water level is measured.

(ii) The maximum amount of _______ dissolved in _______ at a particular temperature is called solubility at that temperature.

(iii) Generally, the density _______ with increase in temperature.

(iv) The solution in which glucose has completely dissolved in water, and no more glucose can dissolve at a given temperature, is called a _______ solution of glucose.

Accepted Answer

(i) The volume of a solid can be measured by the method of displacement, where the solid is _immersed_ in water and the _rise_ in water level is measured.

(ii) The maximum amount of _solute_ dissolved in _solvent_ at a particular temperature is called solubility at that temperature.

(iii) Generally, the density _decreases_ with increase in temperature.

(iv) The solution in which glucose has completely dissolved in water, and no more glucose can dissolve at a given temperature, is called a _saturated_ solution of glucose. — Step-by-step:
(i) Displacement method involves immersing the solid in water and measuring how much the water level rises, which equals the volume of the solid.
(ii) Solubility is defined as the maximum amount of solute dissolved in a solvent at a given temperature.
(iii) Density usually decreases as temperature increases because volume expands.
(iv) When no more solute can dissolve, the solution is saturated.

Question 3

You pour oil into a glass containing some water. The oil floats on top. What does this tell you?

(i) Oil is denser than water

(ii) Water is denser than oil

(iii) Oil and water have the same density

(iv) Oil dissolves in water

Accepted Answer

Correct answer: (ii) Water is denser than oil.

Explanation: Since oil floats on water, it means oil is less dense than water. Therefore, water is denser than oil. — When two liquids do not mix and one floats on the other, the one floating is less dense. Here, oil floats on water, so oil is less dense and water is denser.

Question 4

A stone sculpture weighs 225 g and has a volume of 90 cm³. Calculate its density and predict whether it will float or sink in water.

Accepted Answer

Density = Mass / Volume = 225 g / 90 cm³ = 2.5 g/cm³.

Since the density of water is 1 g/cm³, and the stone's density (2.5 g/cm³) is greater than water, the stone will sink in water. — Step 1: Calculate density using formula:
Density = Mass / Volume
= 225 g / 90 cm³ = 2.5 g/cm³

Step 2: Compare with water density (1 g/cm³):
Since 2.5 > 1, the stone is denser and will sink.

Question 5

Which one of the following is the most appropriate statement, and why are the other statements not appropriate?

(i) A saturated solution can still dissolve more solute at a given temperature.

(ii) An unsaturated solution has dissolved the maximum amount of solute possible at a given temperature.

(iii) No more solute can be dissolved into the saturated solution at that temperature.

(iv) A saturated solution forms only at high temperatures.

Accepted Answer

Correct statement: (iii) No more solute can be dissolved into the saturated solution at that temperature.

Explanation:
(i) Incorrect because a saturated solution cannot dissolve more solute at that temperature.
(ii) Incorrect because an unsaturated solution has less than the maximum solute dissolved.
(iv) Incorrect because saturated solutions can form at any temperature depending on solubility. — Step-by-step:
- Saturated solution means maximum solute dissolved; no more can dissolve.
- Unsaturated solution means more solute can still dissolve.
- Saturated solutions are not restricted to high temperatures; they depend on solubility at that temperature.

Question 6

You have a bottle with a volume of 2 litres. You pour 500 mL of water into it. How much more water can the bottle hold?

Accepted Answer

Total volume of bottle = 2 litres = 2000 mL
Water poured = 500 mL
Remaining volume = 2000 mL - 500 mL = 1500 mL

Therefore, the bottle can hold 1500 mL more water. — Step 1: Convert litres to millilitres (1 litre = 1000 mL)
2 litres = 2000 mL

Step 2: Subtract the volume of water poured from total volume
2000 mL - 500 mL = 1500 mL

Step 3: The remaining volume is the capacity left for more water.

Question 7

An object has a mass of 400 g and a volume of 40 cm³. What is its density?

Accepted Answer

Density = Mass / Volume = 400 g / 40 cm³ = 10 g/cm³. — Using the formula:
Density = Mass / Volume
= 400 g / 40 cm³
= 10 g/cm³

Question 8

Analyse Fig. 9.25a and 9.25b. Why does the unpeeled orange float, while the peeled one sinks? Explain.

Accepted Answer

The unpeeled orange floats because the peel contains air pockets, making its overall density less than water. When the peel is removed, the orange's density increases as the air pockets are lost, making it denser than water, so it sinks. — Step-by-step:
- The peel traps air, reducing the orange's density.
- Lower density than water causes it to float.
- Removing the peel removes air pockets, increasing density.
- Higher density than water causes it to sink.

Question 9

Object A has a mass of 200 g and a volume of 40 cm³. Object B has a mass of 240 g and a volume of 60 cm³. Which object is denser?

Accepted Answer

Density of Object A = 200 g / 40 cm³ = 5 g/cm³
Density of Object B = 240 g / 60 cm³ = 4 g/cm³

Therefore, Object A is denser than Object B. — Calculate density for both objects:
Object A: 200 g / 40 cm³ = 5 g/cm³
Object B: 240 g / 60 cm³ = 4 g/cm³
Compare densities: 5 > 4, so Object A is denser.

Question 10

Reema has a piece of modeling clay that weighs 120 g. She first moulds it into a compact cube that has a volume of 60 cm³. Later, she flattens it into a thin sheet. Predict what will happen to its density.

Accepted Answer

The density of the modeling clay will remain the same whether it is in the shape of a compact cube or a thin sheet because density depends on mass and volume, and the mass remains constant while the volume also remains the same (the clay is just reshaped, not compressed or expanded). — Density = Mass / Volume
Mass is constant (120 g).
Volume remains the same regardless of shape.
Therefore, density remains unchanged.

Question 11

A block of iron has a mass of 600 g and a density of 7.9 g/cm³. What is its volume?

Accepted Answer

Volume = Mass / Density = 600 g / 7.9 g/cm³ ≈ 75.95 cm³. — Using formula:
Volume = Mass / Density
= 600 g / 7.9 g/cm³
≈ 75.95 cm³

Question 12

You are provided with an experimental setup as shown in Fig. 9.26a and 9.26b. On keeping the test tube (Fig 9.26b) in a beaker containing hot water (~70 °C), the water level in the glass tube rises. How does it affect the density?

Accepted Answer

When the test tube is kept in hot water, the liquid inside expands causing the water level in the glass tube to rise. As volume increases with temperature, density decreases because density = mass/volume and mass remains constant while volume increases. — Step-by-step:
- Heating causes expansion of liquid.
- Volume increases.
- Mass remains constant.
- Density = Mass / Volume decreases as volume increases.
- Hence, density decreases with increase in temperature.

Question 13

Which of the following best defines a solution?

Accepted Answer

A homogeneous mixture of two or more substances — A solution is a homogeneous mixture where the solute is uniformly distributed in the solvent at the molecular level, making it appear as a single phase.

Question 14

In a sugar solution, which is the solvent and which is the solute?

Accepted Answer

Water is solvent and sugar is solute — In a sugar solution, water is present in larger amount and acts as the solvent, while sugar is the solute present in smaller amount.

Question 15

Which of the following is NOT a state in which solutions can exist?

Accepted Answer

Plasma solution — Solutions can exist as solid (alloys), liquid (sugar in water), or gas (air). Plasma is not a state in which solutions are classified in this context.

The Amazing World of Solutes, Solvents, and Solutions

The Amazing World of Solutes, Solvents, and Solutions — Study Notes

The Amazing World of Solutes, Solvents, and Solutions

9.1 What Are Solute, Solvent, and Solution?

9.2 How Much Solute Can a Fixed Amount of Solvent Dissolve?

Practice Questions — The Amazing World of Solutes, Solvents, and Solutions

All 13 Chapters in Curiosity